Some aspects of the Martian climate in the Mars Orbiter Laser Altimeter (MOLA) investigation. Part I. Evolution of the polar residual ice caps. Part II. Polar night clouds. Part III. Interpretation of the MOLA reflectivity measurement in terms of the surface albedo and atmospheric opacity
The spacecraft exploration of the planet Mars in the last two decades provided scientists with an enormously rich data base. This work presents some aspects of the Mars Orbiter Laser Altimeter investigation related to the issues in the Martian climatology. The instrument continues to function on board of the Mars Global Surveyor Spacecraft. The polar ice caps on Mars are the largest reservoirs of water on the planet. Their formation and evolution are not understood very well at this point. Ice flow, sublimation and wind erosion are believed to be the most important processes that shape the caps. We have developed a model to understand the role of sublimation for the formation of the ice caps and attempted to constrain the time scale for the formation of the observed ice caps. We argue that sublimation is a very important process for the formation of the caps, especially on the time scales greater than 10 million years. We report the direct observations of CO2 clouds, forming during the polar winter times over both poles. These clouds are similar over both poles and possibly represent a CO 2 snowfall. On the basis of the reflective properties and spatial occurrence, we can distinguish two major classes of clouds. We will discuss some hypotheses on the mechanisms of their formation. Total atmospheric opacity of the Martian atmosphere at 1μ m can be derived from the MOLA reflectivity measurement. Opacity estimates are found to be consistent with the Viking Lander and Pathfinder values. Opacity measured in the polar regions displays storms and polar hood activity. We will derive scale heights for dust and water ice using observations on large topographic structures. Comparison of the MOLA derived opacity with the TES derived opacity yields information on the aerosol particle size distribution. We discuss an algorithm to derive 1μm normal albedo of the surface. 9μm dust opacity from the Thermal Emission Spectrometer (TES) is employed to remove an atmospheric attenuation from the MOLA reflectivity measurements. We will present some initial results on the calculation of the surface albedo.
- Pub Date:
- May 2002
- Physics: Astronomy and Astrophysics, Physics: Atmospheric Science, Geophysics